It has long been known in the disposable absorbent bandage art that it is extremely desirable to construct absorptive devices, such as disposable diapers, sanitary napkins, incontinent devices, absorbent wound dressings, and the like, presenting a dry surface feel to the user to improve wearing comfort and to minimize the development of undesirable skin conditions due to prolonged exposure to moisture absorbed within the bandage. One viable prior art solution to the aforementioned problem is disclosed in U.S. Pat. No. 4,041,951 issued to Sanford on Aug. 16, 1977 and hereby incorporated herein by reference. The Sanford patent discloses a preferred disposable diaper structure comprising a substantially planar, moisture absorbent layer disposed between a soft topsheet and a moisture-resistant backing sheet. The nonwoven fibrous topsheet preferably comprises an integral structure containing a multiplicity of depressed areas which intimately contact the uppermost surface of a substantially planar, moisture absorbent layer. The nondepressed areas of the topsheet contact the wearer's skin in-use. In a particularly preferred embodiment, the nonwoven fibrous topsheet is comprised of a substantially hydrophobic material exhibiting wet resilience such that the topsheet tends to resume its substantially three-dimensional character upon removal of pressure applied against the topsheet by the body movements of the wearer. The nondepressed areas of the topsheet, which are of substantially the same density as the depressed areas, tend to isolate the wearer's skin from moisture contained within the moisture absorbent layer, thereby providing surface dryness and resistance to rewetting when the structure is temporarily subjected to pressure resulting from the wearer's body movements.
U.S. Pat. No. 3,814,101 issued to Kozak on June 4, 1974, attacks the problem of a wet topsheet in a manner slightly different from the use of hydrophobic nonwoven materials. Kozak suggests a topsheet of a nonfibrous, hydrophobic film which is provided with a plurality of valvular slits which restrict the reverse flow of liquid from the absorbent element of the device.
U.S. Pat. No. 3,929,135 issued to Thompson on Dec. 30, 1975, and hereby incorporated herein by reference, suggests a macroscopically expanded three-dimensinal topsheet comprised of liquid-impermeable material, but provided with tapered capillaries, said capillaries having a base opening in the plane of the topsheet and an apex opening remote from the plane of the topsheet, said apex opening being in intimate contact with the absorbent pad utilized in the disposable absorbent bandage.
As utilized herein, the term "macroscopically expanded", when used to describe three-dimensional plastic webs, ribbons and films, refers to webs, ribbons and films which have been caused to conform to the surface of a three-dimensional forming structure so that both surfaces thereof exhibit the three-dimensional pattern of said forming structure, said pattern being readily visible to the naked eye when the perpendicular distance between the viewer's eye and the plane of the web is about 12 inches. Such macroscopically expanded webs, ribbons and films are typically caused to conform to the surface of said forming structures by embossing, i.e., when the forming structure exhibits a pattern comprised primarily of male projections, by debossing, i.e., when the forming structure exhibits a pattern comprised primarily of female capillary networks, or by extrusion of a resinous melt directly onto the surface of a forming structure of either type. By way of contrast, the term "planar", when utilized herein to describe plastic webs, ribbons and films, refers to the overall condition of the web, ribbon or film when viewed by the naked eye on a macroscopic scale. In this context "planar" webs, ribbons and films may include webs, ribbons and films having fine scale surface aberrations on one or both sides, said surface aberrations not being readily visible to the naked eye when the perpendicular distance between the viewer's eye and the plane of the web is about 12 inches or greater. Planar plastic webs of the aforementioned type are known in the art.
The topsheet disclosed in the aforementioned Thompson patent allows the free transfer of fluids from the body into the absorbent element of the device while inhibiting the reverse flow of these fluids. This provides a relatively much drier surface in contact with the user than had been previously obtainable. However, experience has demonstrated that despite the highly effective fluid transfer and fluid isolation characteristics exhibited by plastic topsheets of the type generally disclosed in the Thompson patent and their proven compatibility with the wearer's skin, many users find it psychologically undesirable to employ a material which is perceivably plastic in contact with their skin. It is believed that this user reaction is due partly to the highly regulated tapered capillary pattern on the wearer-contacting surface of the topsheet and partly to the glossy appearance of
The commonly assigned, co-pending U.S patent application of Clifford J. Radel and Hugh A. Thompson entitled RESILIENT PLASTIC WEB EXHIBITING FIBER-LIKE PROPERTIES AND METHOD AND APPARATUS FOR ITS MANUFACTURE, Ser. No. 206,410, filed Nov. 13, 1980, now U.S. Pat. No. 4,342,314 and hereby incorporated herein by reference, discloses an improved macroscopically expanded three-dimensional plastic web which eliminates the regulated pattern of tapered capillaries, as disclosed in the Thompson patent, while preserving the desirable fluid transport properties of the structure. The macroscopically expanded three-dimensional plastic web disclosed in the application of Radel et al. preferably exhibits a fine scale three-dimensional microstructure comprising a regulated continuum of capillary networks, preferably of steadily decreasing size, originating in and extending from one surface of said web and preferably terminating in the form of apertures in the opposite surface thereof to promote rapid liquid transport in the direction of decreasing capillary size. The web's fiber-like appearance is comprised of a continuum of fiber-like elements, each end of said fiber-like elements being interconnected to at least one other of said fiber-like elements. In a particularly preferred embodiment, the interconnected fiber-like elements are substantially non-aligned with respect to one another.
A typical capillary network in the Radel et al. structure comprises an uppermost capillary opening formed by a multiplicity of primary fiber-like elements interconnected to one another in the uppermost plane of the web. The opening may, if desired, be further subdivided into smaller capillary openings by secondary and tertiary fiber-like elements at planes located below the wearer-contacting surface of the web.
Each of the primary fiber-like elements exhibits a substantially uniform U-shaped cross-section along its length. Its cross-section comprises a base portion located in the wearer-contacting plane and a primary sidewall portion joined to each edge of said primary base portion and extending generally in the direction of the absorbent pad-contacting surface of the web. The secondary and tertiary fiber-like elements, when employed, are generally similar, but originate in planes below the wearer-contacting surface of the web. Because the plastic web of Radel et al. is comprised of a multiplicity of interconnected fiber-like elements rather than a continuous, regulated pattern of tapered capillaries, as disclosed in the Thompson patent, its appearance and tactile impression are generally perceived as more fiber-like.
In a particularly preferred embodiment of the Radel et al. invention, the web's visible surface (i.e., that surface which is generally observable from a perspective which is substantially perpendicular to the plane of the web) is also provided with a fine scale texture comprising a multiplicity of generally parallel V-shaped grooves to create a non-planar surface appearance in the web. The Radel et al. application suggests that the ridges and valleys formed in the plastic web by the V-shaped grooves in the forming structure tend to reduce the web's gloss.
The commonly assigned allowed U.S. patent application of Eugene R. Sorensen entitled DISPOSABLE DIAPER HAVING A TEXTURED THERMOPLASTIC FILM TOPSHEET, Ser. No. 225,944 filed on Jan. 19, 1981, now U.S. Pat. No. 4,327,730 and hereby incorporated herein by reference, likewise recognizes the perceived drawbacks associated with a glossy-appearing macroscopically expanded three-dimensional plastic web to be utilized in contact with the skin. Accordingly, the application of Sorenson discloses a macroscopically expanded three-dimensional plastic film provided with a surface texturing treatment. In a particularly preferred embodiment, the film is employed as a diaper topsheet. The texturing treatment preferably provides a multiplicity of "nubbles" integrally formed on at least one surface to "improve the tactile impression of the thermoplastic film and to reduce its gloss". The nubbles, which impart an irregular and unsmooth texture to the wearer-contacting surface of the topsheet, are small protuberances which project outwardly from the wearer-contacting surface of the topsheet. The number, size, and spacing of the nubbles may be varied within a critical range to give differing degrees of irregularity to the wearer-contacting surface. The nubbles are preferably spherical or spheroidal in cross-section, although it is suggested that other cross-sectional shapes may be used.
A preferred method for manufacturing such a topsheet is disclosed in the commonly assigned, co-pending U.S. patent application of Paul R. Louis, Eugene R. Sorenson and Thomas R. Ballard entitled METHOD AND APPARATUS FOR TEXTURING A THERMOPLASTIC FILM, Ser. No. 036,254, filed May 4, 1979 and issued on Mar. 31, 1981 as U.S. Pat. No. 4,259,286, said application and said patent being hereby incorporated herein by reference.
Briefly, Louis et al. employs a perforate tubular forming member having a multiplicity of particles affixed to its outermost or web-contacting surface. In a particularly preferred embodiment, the tubular member is coated with a mixture of said particles and epoxy, which epoxy may be electrostatically sprayed onto said tubular member and thereafter cured. As should be apparent from the foregoing description, the variability in size and spacing of the particles which form the nubbles in the plastic film processed on said tubular forming member is completely random, and will depend upon such factors as the uniformity in size and shape of the particles employed, the ratio of particles to epoxy, and the uniformity of the spraying techniques.
While the striation treatment disclosed in the aforementioned application of Radel et al. and the random particle treatment disclosed in the aforementioned applications of Louis et al. and Sorenson have in certain instances been employed to produce macroscopically expanded three-dimensional plastic webs exhibiting reduced gloss when compared to untreated prior art plastic webs, it is nonetheless an object of the present invention to accurately define the relevant criteria which must be satisfied to ensure that macroscopically expanded three-dimensional plastic webs which satisfy said criteria will exhibit a substantially non-glossy visible surface when the perpendicular distance between the viewer's eye and the plane of the web is about twelve inches or greater.
It is another object of the present invention to accurately define the relevant criteria which must be satisfied to ensure that macroscopically expanded three-dimensional plastic webs which satisfy said criteria will exhibit a substantially non-glossy visible surface and an improved cloth-like or fiber-like tactile impression.
It is another object of the present invention to provide macroscopically expanded, three-dimensional plastic webs which do in fact satisfy the aforementioned criteria.
It is still another object of the present invention to provide method and apparatus for producing plastic webs exhibiting the desirable characteristics described herein.